Impacts of Climate Change on Salmon, part II

1. Impacts of Climate Change on Salmon, part II Harley Soltes/Seattle Times Nate Mantua Ingrid Tohver, and Alan Hamlet JISAO CSES Climate Impacts Group University of Washington

2. What we did Hydrologic models were forced by downscaled precipitation and surface temperature data for “historic”, 2020s, 2040s, and 2080s (Elsner et al.) Using the “VIC model” at 1/16˚ resolution; with multimodel composite A1B and B1 scenarios, respectively We analyzed simulated streamflow records at 97 locations for monthly average patterns, daily peak flows, and 10 day average summer low flows (base flows)

3. Why we chose these factors Peak flows: large flood events reduce egg-to-fry and parr survival rates Summer low flows = rearing habitat for fish with stream type life histories Seasonal runoff patterns are closely related to life history types and the biodiversity of salmon

4. 3 basic streamflow patterns Historical 2080s A1B rain-dominated “transient” basins with an early winter peak from rainfall, and a spring peak from snowmelt snowmelt-dominated basins, where streamflow peaks in late spring and early summer

5. Dramatic changes in snowmelt systems Snowmelt rivers become transient basins Transient basins become rainfall dominant

6. Models project more winter flooding in sensitive “transient runoff” river basins that are common in the Cascades Likely reducing survival rates for incubating eggs and rearing parr

7. Summer base flows are projected to drop substantially (5 to 50%) for most streams in western WA and the Cascades The duration of the summer low flow season is also projected to increase in snowmelt and transient runoff rivers, and this reduces rearing habitat

8. Upwelling food webs in our coastal ocean Cool water, weak stratification high nutrients, a productive “subarctic” food-chain with abundant forage fish and few warm water predators Warm stratified ocean, few nutrients, low productivity “subtropical” food web, a lack of forage fish and abundant predators Recently, warm ocean years have generally been poor for NW chinook, coho and sockeye, but good for Puget Sound pink and chum salmon.

9. Box1 The future will not present itself in a simple, predictable way, as natural variations will still be important for climate change in any location oC Degrees C Overland and Wang EosTransactions (2007)

10. Reduced calcification rates for calcifying (hard-shelled) organisms and physiological stress Shifts in phytoplankton diversity and changes in food webs Reduced tolerance to other environmental fluctuations Potential for changes to fitness and survival, but this is poorly understood Barrie Kovish Pacific Salmon ARCOD@ims.uaf.edu Coccolithophores Copepods Vicki Fabry Pteropods What are the biological implications of ocean acidification? (Slide provided by Dick Feely, NOAA)

11. Floods Warm, low streamflow Impacts summary for salmon Warmer lower flows in summer Acidification, warming, winds?

12. Impacts will vary depending on life history and watershed types Low flows+warmer water = increased pre-spawn mortality for summer run salmon and steelhead Clear indications for increased stress on Columbia Basin sockeye, summer steelhead, summer Chinook, also Lake Washington sockeye and Chinook Increased winter flooding in Puget Sound streams an increased stressor on egg-to-fry survival rates for fall spawners, and overwinter survival rates for yearling parr (steelhead, coho, and stream-type chinook)

13. Impacts of Climate Change on Salmon Recovery in the Snohomish River (Battin et al. 2007: PNAS) Decreasing Spawning Flows • Climate Change will make • salmon restoration more difficult: • Decreasing Summer/Fall Low Flows • Increasing Winter Peak Flows • Increasing water temperatures in critical periods Increasing Winter Flows

14. Mitigating projected impacts Reduce existing threats caused by land/water use that impair natural hydrologic processes Glines Canyon Dam, Elwha River • Protect and restore instream flows in summer • Identify and protect thermal refugia • Reconnect, restore and protect off-channel habitat in floodplains

15. Increased conflict over use of surface water in summer Human demands on surface water are projected to increase during times of high salmon vulnerability

16. Planning for a warmer future The potential for increased conflict over scarce summer water begs for strategic policy thinking that recognizes trade-offs will have to be made Developing clear decision-guidance now may be an effective way to avoid future crises and potentially high-cost conflicts